Note: The muted state of a track isn't useful for what's typically thought of as muting and unmuting a track. Instead, use the enabled property; setting enabled to false causes the track to output only empty frames.

The RTCRtpTransceiver interface has now been implemented, since the Firefox implementation of WebRTC now supports transceivers, with RTCPeerConnection and other interfaces updated to use them per the latest specification.

HTTP authentication now uses utf-8 encoding for usernames and passwords (rather than ISO-8859-1) for parity with other browsers, and to avoid potential problems as described in баг 1419658.

Everyday the HSTS preload list is updated from Google. Normally this doesn't warrant a note, but in this release new TLDs were included, notably .app and .dev. While they are new TLDs developers might have used them for local development and be surprised by this change. Note that reserved TLDs should be used for local development instead.